Coagulation device for coagulating biological tissues

ABSTRACT

Plasma coagulation devices are known in which a generally bare electrode wire is disposed in a tube that can be passed through the working channel of an endoscope until its end arrives in the field of view of the endoscope. Through the tube argon is supplied. A high-frequency current is supplied to produce a coagulation current in the form of an arc in the argon atmosphere between the end of the electrode wire and the portion of tissue to be coagulated. To simplify the arrangement and to improve its performance, in particular by reduction of the resistance to flow, it is proposed to supply the argon directly through the working channel and to use as conductor a wire insulated with thermally stable material, which at its end comprises a discharge section with a protective device to prevent a damaging direct flow of current into the portion of tissue to be coagulated.

FIELD OF THE INVENTION

The invention relates to a coagulation apparatus, in particular a plasmacoagulation apparatus.

BACKGROUND OF THE INVENTION

The German patent DE 37 10 489 C2 discloses a plasma coagulationapparatus intended for use in open surgery. In this apparatus argon isejected from a nozzle in the center of which is a discharge electrode,with sufficient pressure and flow velocity that in addition to thecoagulation effect produced by an arc formed between the electrode andthe tissue to be coagulated, fluids “floating” on the tissue are pushedaway. With this arrangement the risk of embolism is very high.Furthermore, it is extremely problematic to use this apparatus in bodycavities because the large amounts of gas typically introduced in thecavities can lead to undesired insufflation effects.

A coagulation apparatus for use in an endoscope is known from U.S. Pat.No. 5,207,675. In this apparatus a tube, within which an electrode isslidably disposed, is inserted into the working channel of an endoscopein such a way that it can be manipulated within said channel by means ofa handle, like an (ordinary) instrument. The electrode, which shouldsimultaneously be constructed as an instrument, is kept in a state suchthat it projects from the tube when in the working (coagulating) mode,in which argon is expelled from the tube that houses the electrode.While in this state, if the electrode touches the tissue to becoagulated, considerable tissue damage can result. In the case ofthin-walled tissues, the consequences (rupture, etc.) can be fatal.

In DE 195 35 811 A1 a coagulation apparatus of the kind cited above isdescribed that goes some way toward avoiding the substantial problemsassociated with the arrangements just described. In particular, the endof the tube housing the electrode is so constructed that there is nodanger of embolism even when a relatively strong gas stream is applied,during which time the electrode is withdrawn into the gas-emitting tubefar enough that it cannot make direct contact with the tissue. However,this arrangement is relatively complicated to manufacture.

The object of the invention is to disclose a coagulation apparatus thatensures increased safety in use and improved operation, while reducingthe manufacturing complexity and cost.

SUMMARY OF THE INVENTION

An essential point of the invention is that it departs completely fromthe idea that (noble) gas must be aimed directly at the site wherecoagulation is occurring, i.e. by means of a tube within which thecurrent-supplying electrode is disposed. Instead, in the presentinvention the working channel itself is used as a conduit to transportthe gas, while the electrode can be constructed as a fully insulatedwire with no lumen. Surprisingly, it has been found that nodisadvantageous effects are introduced by the fact that the gas emergesfrom an end of the working channel proximal to the distal end of theconductor—that is, proximal to the discharge section—and that thedischarge section occupies no precisely specified position with respectto the end of the working channel, from which the gas emerges. On theother hand, it is considerably simpler to construct the conductor as aninsulated wire without a lumen, which reduces the costs of manufactureand enables disposable conductors to the used. This in turn reduces therisk of infection.

Furthermore, conductors without a lumen are not only simpler tomanufacture but, because conductors have small diameters it's possiblefor the coagulation apparatus incorporating such conductors to befurther miniaturized as a whole. At the same time, however, aconsiderably larger cross section for flow through the gas-supplyconduit is ensured, which offers the advantage that the regulation ofthe gas supply can be substantially improved in the simplest possiblemanner. That is, the gas pressure at the distal end of the workingchannel can be assumed to differ only negligibly from the gas pressureat its proximal end, because with the large flow cross sectionsachievable here, only a slight pressure drop (given the customary, nottoo large flow velocities) is to be expected. Hence it is possiblesimultaneously (with appropriate regulation of the gas-supply pressure)to eliminate in advance the danger that, if the gas does not flow awayas intended, an uncontrolled, damaging insufflation will occur.

With absolute certainty the possibility is avoided that an excessivelystrong laminar gas stream will strike the region of the tissue to becoagulated, which, as mentioned, could cause an embolism.

Preferably the conductor comprises at least one wire, which by means ofa closely apposed layer of insulation is insulated in particular fromthe endoscope, i.e. the wall of the working channel. The arrangementdescribed here is thus particularly simple to manufacture. Preferably inthis case the wire is chosen to be stiffly elastic so that proximalfixation of the conductor also ensures adequate fixation of its distalend and hence of the discharge section. It is therefore not necessary toguide the conductor so that it is precisely coaxial with the workingchannel and, in particular, to keep it exactly in position in the endregion, because—surprisingly—the preferably gently outflowing current ofnoble gas forms a kind of “cloud” that fills the region between thedischarge section and the tissue to be coagulated.

The layer of insulation is preferably so constructed that a specificcapacitance, preferably matched to the frequency of the coagulationcurrent, is produced between conductor and wall, so that optimalperformance can be ensured. In particular, the capacitance (straycapacitance) between conductor and wall should be kept very low in orderto minimize losses.

Preferably the insulation layer consists of thermally stable material,in particular polytetrafluoroethylene or a similar plastic resistant tohigh temperatures.

The protective device is preferably so constructed that a substantiallyundirected discharge at the discharge section is ensured. This measureis intended to make certain that the discharge current flows between thedischarge section and a section of the tissue with a relatively highmoisture content and hence a relatively low resistance (per unit area).As a result, it is ensured that the coagulation current “finds its way”automatically from the discharge section. An especially uniform andrapid coagulation effect can thus be guaranteed.

There are various possible ways to construct the protective device insuch a way that no excessively large, potentially damaging coagulationcurrents will flow.

In a first embodiment of the invention the protective device is formeddirectly by the insulation layer, inasmuch as the ends thereof projectbeyond the current-conducting part (in the direction of the conductor).Many geometrical shapes are conceivable here.

the protective device can be constructed as a separate part, inparticular as a sheath-, ball- or basket-shaped part made of insulating,thermally stable material. Ceramic material is especially suitable forthis purpose.

Preferably the discharge section comprises substantially punctate ortip-shaped discharge electrodes. This measure ensures easy ignition ofthe plasma owing to the high field strengths at the pointed tips. Italso increases safety in operation, because it is not necessary to usetoo-high voltages to trigger the discharge.

In an especially preferred embodiment of the invention the dischargesection comprises a plurality of discharge electrodes arranged inparallel electrically and substantially defining a continuous surface,in which the electrodes are substantially equidistant from one anotherand separated by layers of insulation. When such uniformly distributed,punctate electrodes are used, which in addition are disposedsubstantially in a plane or in a convex surface, preferably flush withthe end surface of the insulation, it is ensured that even if theelectrodes make direct contact with the tissue, no serious damage to thetissue will result. The reason is that with an arrangement of this kinda substantially hemispherical current distribution is formed in theregion of the contact area of each punctate electrode (the contact islimited to the surface of the tissue and the electrode cannot penetrateinto the tissue), which in turn causes the current density to become solow, even a very short distance away from the electrode, that no serioustissue damage can occur. In the direct contact region, where the currentdensity is still relatively high and the liquid contained in the tissuevaporizes, the resistance rises very rapidly, so that the current flowis completely cut off. Because a plurality of individual electrodes isprovided it can be ensured that a uniform plasma coagulation currentflows over a relatively large area.

Preferably fixation and/or adjustment devices are provided, inparticular at the proximal end of the endoscope, and are so constructedthat the discharge section is positioned in the field of view of theobservation optics of the endoscope.

In another preferred embodiment of the invention the fixation andadjustment devices are constructed in the manner custormary forinstruments that can be introduced into the working channel ofendoscopes and can be moved or manipulated while projecting out of thedistal end of said channel. The actual manipulation mechanism issituated at the end of the endoscope away from the patient and is soconstructed that the distal end of the conductor with the dischargesection can be moved within the field of view of the endoscope. In thisway a precise treatment of the tissue can be carried out, while theendoscope is immobile relative to the tissue.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, preferred embodiments of the invention are describedwith reference to drawings, wherein

FIG. 1 is a schematic partially sectional view of an endoscope withpartially opened working channel,

FIG. 2 shows a first embodiment of a discharge section with protectivedevice in longitudinal section,

FIG. 3 shows a second embodiment of a discharge section with protectivedevice in longitudinal section,

FIG. 4 shows a third embodiment of a discharge section with protectivedevice in longitudinal section,

FIG. 5 shows a fourth embodiment of a discharge section, with aplurality of electrodes in longitudinal section,

FIG. 6 is a view of the discharge section according to FIG. 5 along theline VI—VI,

FIG. 7 is a view of a fifth embodiment of a discharge section, with aplurality of electrodes in longitudinal section, and

FIG. 8 is a side view of the discharge section according to FIG. 7.

DETAILED DESCRIPTION

In the following description, the same reference numerals are used foridentical parts or parts with identical actions.

In FIG. 1 a highly schematic side view of an endoscope 10 is shown,which in a manner known per se comprises a working channel 11, whichextends from a proximal working-channel end 14 to a distalworking-channel end 13. At the distal end of the endoscope 10 an optic12 is provided, through which objects in the region of a field of viewB, in particular tissue G to be coagulated, are imaged, in general on atelevision screen. In the present case, for purposes of illustration anocular 16 at the proximal end of the endoscope 10 is shown.

At the proximal end 14 of the working channel 11 a Y-piece 15 isdisposed, by way of which, firstly, a conduit 21 is connected in agas-tight manner. The conduit 21 leads to an argon source 20 thatcomprises regulatory devices (not shown) in order to allow apre-adjustable, uniform current of argon gas to flow into the proximalend 14 of the working channel 11, so that at the distal working-channelend 13 the argon flows out uniformly with low velocity, as a “turbulentcloud”, and fills the region between a tissue G to be coagulated and adistal discharge section 40, which forms the end of a conductor 30. Theconductor 30 in turn runs through the working channel 11 and extends (byway of a sealing element) through the Y-piece 15 to an HF source 23. TheHF source 23 is constructed in a manner known per se and enables ahigh-frequency coagulation current to be sent through the conductor 30to the discharge section 40. HF generators of this kind are commerciallyobtainable.

In the following, particular embodiments of the discharge section willbe described in more detail with reference to FIGS. 2 to 6.

From FIGS. 2 to 4 it can be seen that the conductor 30 comprises a wire32 enclosed in an insulation layer 31, preferably made of PTFE. The wire32 with the surrounding insulation layer 31 is sufficiently stiff that,as shown in FIG. 1, it is held by the immobilizing Y-piece 15 at theproximal end in a position such that its discharge section 40 is kept ina specific position within the field of view B of the optic 12, so thatthe latter position remains substantially constant even during movementof the endoscope 10.

In the embodiment of the invention shown in FIG. 2 the wire 32 is sodisposed as to project beyond the end of the insulation layer 31, sothat a discharge electrode 41 is formed. Preferably this electrode ispinched off or sharpened in such a way as to produce sharp edges, atwhich the electrical field strength (as is known per se) is very high,so that ignition of the plasma is possible even with relatively lowvoltages.

Now, in order to prevent the discharge electrode 41 from coming intodirect, current-conducting contact with the tissue G to be coagulated,which could produce serious and dangerous tissue damage (or evenrupture, in the case of thin tissue layers), a protective device 50 inthe form of a basket 51 is provided, which in this case is made ofnon-conducting ceramic material that is resistant to high temperatures.The basket 51 comprises openings 52 so that direct gas contact ispossible between the external surroundings and the interior of thebasket, and a substantially undisturbed current flow through a plasmacan develop.

In the embodiments of the invention shown in FIGS. 3 and 4 theprotective device 50 is formed by the material of which the insulationlayer 31 is composed. In the embodiment of the invention shown in FIG.3, the discharge section 50 is partially cut away for this purpose sothat its end is concave and the discharge electrode 41 is situated atthe base of the concavity; the edge 54 of the concavity projects in thedistal direction beyond the discharge electrode 41. This arrangementensures that no direct contact can occur between the discharge electrode41 and a tissue G to be coagulated.

In the embodiment shown in FIG. 4 the principle is similar but the edge54 is not smooth; instead it comprises a row of teeth 53, which likewiseprevent direct contact between the discharge electrode 41 and the tissueG to be coagulated.

The preferred embodiment of the invention shown in FIGS. 5 and 6 isbased on a different principle for the protective device 50. In thisarrangement a whole bundle of conductors 32 ₁, 32 ₂, . . . , 32 _(n)with surrounding insulation layers 31 ₁, 31 ₂, . . . , 31 _(n) isprovided, in which the conductors 32 are connected in parallel to the HFsource 23. The conductors 30 are cut off at the distal end so as todefine a planar surface (in another embodiment, a convex surface), sothat the ends of the wires 32 form punctate discharge electrodes 41 ₁,41 ₂, . . . , 41 _(n) that are flush with the end surfaces of theinsulation layers 31. If such an end surface, formed by an area ofinsulation within which punctate discharge electrodes 41 areequidistantly distributed (as shown in FIG. 6), comes into contact witha tissue G, the resulting current flow extends hemispherically from eachof the punctate contact sites, such that the current density decreasesas the reciprocal of the third power of the distance from the punctateelectrode. As a result it is ensured that even at very small depthswithin the tissue an “innocuous” current density prevails.

the embodiment of the invention shown in FIG. 7 a plurality of punctatedischarge electrodes 41 ₁, 41 _(n) is again provided, which are flushwith the end surface of an insulation layer 31′. The insulation layer31′ in this case is constructed as a ceramic part in which the dischargeelectrodes are embedded in the form of filling. This arrangement ensuresthat—as shown in FIG. 8—an area relatively densely packed with dischargeelectrodes 41 is produced, so that the plasma discharge can be generatedat the discharge section 40 in an undirected manner. In anotherembodiment of the invention, not shown here, the discharge section 40 ismade of a (metallic) conductor piece coated with a thin insulating layerin which small openings or holes are made, to form the punctatedischarge electrodes.

It will be evident from the above that an essential point of the presentinvention lies in the fact that it no longer employs—as was previouslycustomary—a “tube” with electrode or current-supply device containedtherein, through which the noble gas is “blown” directly into the regionin which the discharge is to occur; instead, the working channel itselfis used and the noble gas is, so to speak, unspecifically (with respectto the discharge region) supplied. In turn, the site from which thedischarge “begins” is precisely specified and can very easily beadjusted, so that the operating physician has control of the coagulationprocess substantially without difficult manipulations.

What is claimed is:
 1. Coagulation apparatus comprising an endoscopeworking channel with a proximal opening and a distal opening and aninner surface extending between the proximal and distal openings; acurrent-supply device with a conductor to conduct a coagulation currentfrom a source to a discharge section at a distal end of the conductor; agas-supply conduit to guide gas from a gas source to a space between thedischarge section and a portion of tissue to be coagulated; a protectivedevice at the discharge section to prevent a damaging direct flow ofcurrent between the discharge section and the portion of tissue to becoagulated; wherein the gas-supply conduit is formed by the endoscopeworking channel, and the conductor passing through the endoscope workingchannel and having an outer insulating layer, which is spaced radiallyinwardly from the inner surface of the endoscope working channel atleast in the vicinity of the distal opening, the distal end of theconductor projecting out of the distal opening with its distal end andits discharge section, in such a way that gas emerging through thedistal opening flows around the distal end of the conductor and thedischarge section as it passes into the space between the dischargesection and the portion of tissue to be coagulated.
 2. Coagulationapparatus according to claim 1, characterized in that the conductor (30)comprises at least one wire (32) that is insulated, in particular withrespect to the endoscope (10) or the wall of the working channel (11),by means of the closely apposed insulation layer (31).
 3. Coagulationapparatus according to claim 2, characterized in that the at least onewire is stiffly elastic in such a way that a proximal fixation of theconductor ensures adequate fixation of the discharge section. 4.Coagulation apparatus according to claim 2, characterized in that theinsulation layer (31) is made sufficiently thick that a specifiedcapacitance, preferably matched to the frequency of the coagulationcurrent, is produced between conductor and wall.
 5. Coagulationapparatus according to claim 2, characterized in that the insulationlayer is made of thermally stable material, in particular ofpolytetrafluoroethylene.
 6. Coagulation apparatus according to claim 1,characterized in that the protective device is so constructed as toensure a substantially undirected discharge at the discharge section. 7.Coagulation apparatus according to claim 1, characterized by amanipulation mechanism so constructed and so disposed in functionalconnection with the conductor that the distal end of the conductor canbe moved in the manner of an endoscope operating instrument. 8.Coagulation apparatus comprising: an endoscope working channel with aproximal opening and a distal opening; a current-supply device with aconductor to conduct a coagulation current; a gas-supply conduit toguide gas from a gas source through the endoscope working channeltowards a portion of tissue to be coagulated; the conductor having aninsulation layer and at least one wire embedded in the insulation layer,which has a distal end extending beyond a distal discharge section ofthe one wire to prevent a damaging direct flow of current between thedistal discharge section and the portion of tissue to be coagulated, thegas emerging through the distal opening flows around the distal end ofthe insulation layer as it passes into the space between the distal endand the portion of tissue to be coagulated.
 9. Coagulation apparatusaccording to one of the preceding claims, characterized in that theprotective device (50) is formed as a separate part made of insulating,thermally stable material, in particular of ceramic.
 10. Coagulationapparatus comprising an endoscope working channel with a proximal and adistal opening; a current-supply device with a conductor to conduct acoagulation current from a source to a discharge section at a distal endof the conductor; a gas-supply conduit to guide gas from a gas source toa space between the discharge section and a portion of tissue to becoagulated; the conductor having substantially sharp-tipped dischargeelectrodes and a protective device at the discharge section to prevent adamaging direct flow of current between the discharge section and theportion of tissue to be coagulated; wherein the gas-supply conduit isformed by the endoscope working channel, and the conductor passingthrough the endoscope working channel projects out of the distal openingthereof with its end and its discharge section, in such a way that gasemerging through the opening flows around the distal end of theconductor and the discharge section as it passes into the space betweenthe discharge section and the portion of tissue to be coagulated. 11.Coagulation apparatus according to claim 10, characterized in that aplurality of discharge electrodes is provided, disposed so as to beelectrically in parallel and substantially to define a continuoussurface.
 12. Coagulation apparatus according to claim 11, characterizedin that the discharge electrodes are disposed in a plane. 13.Coagulation apparatus according to claim 11, characterized in that thedischarge electrodes are disposed in a convex surface.
 14. Coagulationapparatus according to claim 10, characterized in that the dischargeelectrodes are disposed substantially flush with an insulation layer.15. Coagulation apparatus according to claim 10, characterized in thatthe discharge electrodes comprise a plurality of insulated individualwires, each of which forms a planar surface at its end.